Business owners and marketers spend a lot of time getting customers to opt-in or subscribe to their email newsletters and lists. However, they often don’t exert the same effort to ensure that these customers they worked so hard to get stay engaged. And then they are puzzled (and annoyed) when that “unsubscribed” notification shows up in their in box.

So what can your organization do to keep customers from unsubscribing from your email lists? Here are the top seven reasons people opt out of email and what you can do to keep customers from clicking that ‘unsubscribe’ button.

1. They never signed up, or didn’t realize they signed up, for your email list.

“The number one reason why [people] see high unsubscribe rates is because of poor list-building tactics,” says Brett Farmiloe, a MailChimp expert and the founder of Markitors. “People think it's OK to buy, rent, scrape and add customers to their lists, and it's not. In fact, it's against MailChimp's terms of service to import third party lists,” he says. And “there's a good reason why: People hate unsolicited email. There's not a faster way to get people to unsubscribe than to add them to your list without their [consent or] confirmation.”

“Consumers [typically] unsubscribe [from email lists] because they didn't realize they subscribed in the first place,” says Daniel Burstein, director of editorial content at MarketingSherpa. “Some businesses add people to their email lists with italicized mice type at the bottom of a form and customers don't even know they are signing up. They think they are just registering for a sweepstakes or downloading a white paper.” The solution: “Clearly communicate to customers that they are subscribing to an email list by providing an opt-in checkbox on forms, along with an error message if they don't complete the checkbox (if subscription is required to receive the incentive),” says Burstein.

2. You’re emailing them too often.

“The [other] frequent reason that people unsubscribe from email is that the email marketer underestimates or overestimates the frequency which subscribers wish to hear from them,” says Ros Hodgekiss, design community manager at Campaign Monitor. “According to a recent survey, 53 percent of consumers reported getting too many emails from retailers, while only 44 percent said they get the right amount.” However, “there are simple ways to get around this issue,” she says. “First of all, you can have your subscribers submit their email frequency preferences, either [when they] subscribe, or later, via an email preference center or similar. This approach puts the power into your subscribers' hands,” she explains, which has proven to be an effective way of holding onto them.

[Typically, according to Campaign Monitor’s research, “sending an email every two weeks is the sweet spot for subscriber engagement.”]

“Secondly, periodically survey your subscribers to find out more about them, which I recommend, for reasons beyond simply learning how to become a better sender.”

3. They can’t properly view your email.

“Just because your email looks good when you test it on your own accounts doesn't mean it's going to be perfect on all of your audience's email platforms,” says Austin Paley, corporate marketing communications manager, Blue Fountain Media.

In particular, beware of “image-heavy emails – emails that look like a poster more than an email,” says Philip Storey, head of global strategy & insights consulting, Lyris, a provider of digital marketing solutions. “Over 50 percent of emails are opened on mobile devices, and mobile devices struggle to download images,” he explains. “Therefore, if you hide your awesome value proposition in an image, people won't see the content and are more likely to unsubscribe.” Therefore, if you don’t want people deleting your emails, or worse, unsubscribing, “make sure that your email renders correctly across all devices,” says Paley. “Using a tool like Litmus is incredibly helpful because it allows you to see how your mailer looks across all platforms, so that you can tweak code accordingly if there are any issues.” Or just make sure that the email template or campaign manager you use is mobile friendly.

4. Your email is too cluttered or looks unprofessional.

“If an email blast looks messy or unprofessional, people will think of it as spam and unsubscribe,” says Gianna Kagel, co-owner, Assisting Hands, a home healthcare agency in New Jersey. To fix this problem, try using a service such as “MailChimp or Constant Contact, and send yourself the email [first] to see how it looks before you send it to your marketing list. If the formatting looks off or you notice any typos, fix it before you let your consumers see it,” she says. “Having someone proofread the email before you send it is always a good idea as well.”

“Not everyone is a designer, but if your email isn't aesthetically pleasing or looks dated, you're sending [the] message: I don't care enough about my business to have good branding, or I don't care enough about your email reading experience to make this pretty and easy to read for you,” adds Summer Brighton, creative director at Summer Brighton. Her solution, like Kagel’s (and many others): “Use an email marketing service [that has] templates you can customize. Or find a graphic designer to put something together for you.” Just “make sure that your branding and messaging is clean, current and nice to look at,” says Brighton.